1 files changed, 90 insertions, 0 deletions
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
new file mode 100644
index 000000000000..ff3c3101d003
--- /dev/null
+++ b/arch/x86/kernel/livepatch.c
@@ -0,0 +1,90 @@
+/*
+ * livepatch.c - x86-specific Kernel Live Patching Core
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/page_types.h>
+#include <asm/elf.h>
+#include <asm/livepatch.h>
+
+/**
+ * klp_write_module_reloc() - write a relocation in a module
+ * @mod:	module in which the section to be modified is found
+ * @type:	ELF relocation type (see asm/elf.h)
+ * @loc:	address that the relocation should be written to
+ * @value:	relocation value (sym address + addend)
+ *
+ * This function writes a relocation to the specified location for
+ * a particular module.
+ */
+int klp_write_module_reloc(struct module *mod, unsigned long type,
+			   unsigned long loc, unsigned long value)
+{
+	int ret, numpages, size = 4;
+	bool readonly;
+	unsigned long val;
+	unsigned long core = (unsigned long)mod->module_core;
+	unsigned long core_ro_size = mod->core_ro_size;
+	unsigned long core_size = mod->core_size;
+
+	switch (type) {
+	case R_X86_64_NONE:
+		return 0;
+	case R_X86_64_64:
+		val = value;
+		size = 8;
+		break;
+	case R_X86_64_32:
+		val = (u32)value;
+		break;
+	case R_X86_64_32S:
+		val = (s32)value;
+		break;
+	case R_X86_64_PC32:
+		val = (u32)(value - loc);
+		break;
+	default:
+		/* unsupported relocation type */
+		return -EINVAL;
+	}
+
+	if (loc < core || loc >= core + core_size)
+		/* loc does not point to any symbol inside the module */
+		return -EINVAL;
+
+	if (loc < core + core_ro_size)
+		readonly = true;
+	else
+		readonly = false;
+
+	/* determine if the relocation spans a page boundary */
+	numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
+
+	if (readonly)
+		set_memory_rw(loc & PAGE_MASK, numpages);
+
+	ret = probe_kernel_write((void *)loc, &val, size);
+
+	if (readonly)
+		set_memory_ro(loc & PAGE_MASK, numpages);
+
+	return ret;
+}